Distributed simulcast architecture

ABSTRACT

A system and method for providing communication in a distributed LMR system architecture is provided herein, wherein the system includes a plurality of LMR subsystems interconnected by a data network. In some embodiments, a subsystem may include a distributed simulcast architecture comprising a plurality of LMR sites, each site having a subsystem controller and a plurality of repeaters. In one embodiment, one subsystem controller operates in an active mode and the remaining subsystem controllers operate in standby to provide redundancy. The repeaters include integrated voter comparator and simulcast controller functionality and circuitry. In some embodiments, the repeaters are operable in an active or standby mode, wherein repeaters in the active mode perform voter comparator and simulcast controller functionality. The distributed simulcast architecture provides simulcast controller and voter comparator redundancy, network failure redundancy, and site redundancy.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. §119(e), this application claims priority from,and hereby incorporates by reference for all purposes, U.S. ProvisionalPatent Application Ser. No. 61/790,588, entitled “Distributed SimulcastArchitecture,” filed Mar. 15, 2013, and naming Arindam Roy and LarryEmmett as inventors.

FIELD

The present disclosure relates generally to communication systems. Morespecifically, but not by way of limitation, the present disclosurerelates to a system and method for providing communication in adistributed simulcast architecture in a Land Mobile Radio (LMR)communication system.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Land Mobile Radio (LMR) systems are deployed by organizations requiringinstant communication between geographically dispersed and mobilepersonnel. Current LMR systems can be configured to provide for radiocommunications between one or more sites and subscriber radio units inthe field. A subscriber radio unit (hereinafter “radio”) may be a mobileunit or a portable unit. LMR systems can be as simple as two radio unitscommunicating between themselves over preset channels, or they can becomplex systems that include hundreds of radio units and multiple sites.Typical users of LMR systems include police departments, firedepartments, medical personnel, security personnel, EMS, and themilitary.

Conventional and trunking LMR system architecture may include multipleLMR sites, each utilizing various equipment including, for example,dedicated site controllers, repeaters, voter comparator and simulcastcontrollers. Specifically, in simulcast system architecture, a primesite is deployed that hosts the site controllers, simulcast controllersand voter comparators. As the LMR system expands, additional equipmentis needed, which becomes increasingly expensive to provide and maintain.Furthermore, each site in the LMR system is often controlled byequipment located at one of the sites comprising the LMR system or bythe equipment located at the prime site. Accordingly, when suchequipment fails, corresponding portions of the LMR system also fail. Assuch, conventional and trunking LMR system architecture lacks redundancyand, therefore, is often subject to single points of failure, therebycompromising the integrity of the LMR system architecture.

SUMMARY

In one embodiment, the present disclosure provides a system forproviding communication in a distributed LMR system architecture, thedistributed LMR system architecture comprising one or more subsystems incommunication with a data network, the system comprising: one or moreLMR sites comprising at least one of the one or more subsystems; one ormore subsystem controllers disposed at each of the one or more LMR sitescomprising the at least one subsystem, each subsystem controller havingat least an active mode and a standby mode, wherein at least onesubsystem controller is operable in the active mode to controlcommunication between the one or more LMR sites in the at least onesubsystem; and one or more repeaters disposed at each of the pluralityof sites in the at least one subsystem, each of the repeaters operableto provide a communication channel, wherein each repeater has at leastan active mode and a standby mode, and wherein at least one repeater isoperable in the active mode to perform at least one of a simulcastcontroller operation and a voter comparator operation.

In another embodiment, the present disclosure provides a method forproviding communication in a distributed land mobile radio (LMR) systemarchitecture, the distributed LMR system architecture comprising one ormore subsystems in communication with a data network, the methodcomprising: providing a subsystem controller in each of a plurality ofLMR sites comprising one of the subsystems, each subsystem controllerhaving at least an active mode and a standby mode; operating one of thesubsystem controllers in the active mode to control communicationbetween the plurality of LMR sites; operating the remaining subsystemcontrollers in the standby mode; providing a plurality of repeaters ateach of the plurality of LMR sites comprising the subsystem, eachrepeater having at least an active mode and a standby mode; operating atleast one of the repeaters in the active mode to perform at least one ofa simulcast controller operation and a voter comparator operation; andoperating the remaining repeaters in the standby mode.

Further embodiments and apparatuses, including other areas ofapplicability, will become apparent from the description providedherein. It should be understood that the description and specificexamples are intended for purposes of illustration only and are notintended to limit the scope of the present disclosure in any manner

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of various embodiments of the presentinvention and the advantages thereof, reference is now made to thefollowing brief description, taken in connection with the accompanyingdrawings and detailed description, wherein like reference numeralsrepresent like parts, and in which:

FIG. 1 illustrates an example embodiment of a centralized LMRarchitecture;

FIG. 2 illustrates an example embodiment of a conventional LMR system;

FIG. 3 illustrates an example embodiment of a trunked LMR system;

FIG. 4 illustrates an example embodiment of a hybrid LMR system;

FIG. 5 illustrates an example embodiment of a simulcast LMR system;

FIG. 6 illustrates an example embodiment of an LMR system incorporatinga distributed architecture;

FIG. 7 illustrates an example embodiment of the first trunked LMRsubsystem provided in FIG. 6;

FIG. 8 illustrates an example embodiment of the second trunked LMRsubsystem provided in the distributed architecture of FIG. 6;

FIG. 9 illustrates an example embodiment of one of the simulcast LMRsubsystems provided in the distributed architecture of FIG. 6;

FIG. 10 illustrates an example embodiment of system for providingreceiver voting in a centralized architecture;

FIG. 11 illustrates an example embodiment of a system for providingreceiver voting in a distributed architecture;

FIG. 12 illustrates an example embodiment of system for providingsimulcast communication in a centralized architecture;

FIG. 13 illustrates an example embodiment of a system for providingsimulcast communication in a distributed architecture;

FIG. 14 illustrates an example embodiment of a centralized simulcastsubsystem;

FIG. 15 illustrates an example embodiment of a trunked simulcastsubsystem in a distributed architecture;

FIG. 16 illustrates an example embodiment demonstrating simulcastcontroller and voter comparator redundancy in a distributed simulcastLMR architecture;

FIG. 17 illustrates an example embodiment demonstrating network failureredundancy in a distributed simulcast LMR architecture; and

FIG. 18 illustrates an example embodiment demonstrating site redundancyin a distributed simulcast LMR architecture.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following detailed description and accompanying drawings,numerous specific details are set forth to provide a thoroughunderstanding of the present disclosure. However, those skilled in theart will appreciate that the present disclosure may be practiced, insome instances, without such specific details. In other instances,well-known elements have been illustrated in schematic or block diagramform in order not to obscure the present disclosure in unnecessarydetail. Additionally, for the most part, specific details, and the like,have been omitted inasmuch as such details are not considered necessaryto obtain a complete understanding of the present disclosure, and areconsidered to be within the purview of persons of ordinary skill in therelevant art.

It is further noted that, unless indicated otherwise, all functionsdescribed herein may be performed in hardware or as softwareinstructions for enabling a computer, radio, or other device to performpredetermined operations, where the software instructions are embodiedon a computer readable storage medium, such as RAM, a hard drive, flashmemory, or other type of computer readable storage medium known to aperson of ordinary skill in the art. In certain embodiments, thepredetermined operations of the computer, radio, or other device areperformed by a processor such as a computer or an electronic dataprocessor in accordance with code such as computer program code,software, firmware, and, in some embodiments, integrated circuitry thatis coded to perform such functions. Furthermore, it should be understoodthat various operations described herein as being performed by a usermay be operations manually performed by the user, or may be automatedprocesses performed either with or without instruction provided by theuser.

An LMR system may employ a centralized architecture whereby various LMRsubsystems are connected by a central network controller and associatednetwork equipment. FIG. 1 illustrates an example of a centralized LMRarchitecture 100, which includes various LMR subsystems 110, dispatchstations 115, and gateway equipment 120 connected by a central networkcontroller 125. The central network controller 125 includes equipmentfor operating and controlling each of the various LMR subsystems 110,dispatch stations 115, and gateway equipment 120. The various LMRsubsystems 110 may include any of a conventional LMR system, trunkingLMR system, hybrid LMR system, or wide area systems such as a simulcastLMR system or multicast LMR system. Examples of such LMR systems arebriefly discussed below with reference to FIGS. 2-5.

FIG. 2 illustrates an example of a conventional LMR system 200.Conventional systems are typically deployed in regions covering largegeographic areas and/or comprising a moderate quantity of users. In aconventional system, a dedicated repeater channel is provided for systemuser groups, and the user chooses the channel or channels on which hewishes to communicate. Often, system user groups are organized based onresponsibility, such as Fire, Police, EMS, Public Works, and Mutual Aid.In most cases, each of these groups has a corresponding dedicatedrepeater channel 202, which provides a frequency for communicating acall.

FIG. 3 illustrates an example of a trunked LMR system 300. Trunkedsystems are typically deployed in regions covering moderate geographicalareas and/or comprising a large quantity of users. Trunked systems havea shared pool of repeater channels for use among system user groups. Therepeater channels at each site are divided into a control channel 302and multiple voice channels 304. The control channel 302 registers aradio into the system and dynamically coordinates radio talkgroupPush-to-Talk (PTT) with an available voice channel.

In a trunked radio system, system talkgroups are often organized basedon responsibility, such as Fire, Police, EMS, Public Works, and MutualAid. The user selects the talkgroup with which he wishes to communicate,and the trunked system then allocates the radio channel used for thevoice transmission. For LMR systems having multiple groups with accessto multiple channels at each site, a trunked system may be implementedto increase the system's efficiency.

A hybrid system combines conventional and trunked repeater channels intoa single system. In hybrid systems, users can be organized functionallyfor either the conventional or trunked part of the system, as needed.FIG. 4 illustrates an example embodiment of a hybrid LMR system 400,which includes a conventional site 410 and a trunked site 420.

In addition to the foregoing, LMR system types may include wide areasystems, which, in some embodiments, are designed to enable radios tomove throughout an area without their users needing to change channelswhile roaming. A simulcast system is an example of a wide area system.An example of a simulcast system 500 is illustrated in FIG. 5. Thesimulcast system 500 includes a single master site 510 (also referred toherein as a prime site) and multiple radio sites 520. The master site510 synchronizes the system timing so that calls are transmittedsimultaneously to all sites for a given repeater channel. Thus, a callis transmitted simultaneously to all sites at the same frequency. Thissynchronization reduces the quantity of frequencies needed for thesystem and simplifies frequency coordination.

Another example of a wide area LMR system is a multicast system. Inmulticast systems, different transmitters within adjacent geographicareas communicate on different radio channel frequencies. The multicastsystem switches the user to the proper channel automatically. Themulticast system configuration offers similar coverage advantages of asimulcast system at a reduced cost. However, multicast systems requiremultiple frequencies, and their users need to change mobile channels asthey move between sites.

Referring again to FIG. 1, the central network controller 125 includesequipment for operating and controlling each of the various LMRsubsystems 110, dispatch stations 115, and gateway equipment 120. As theLMR system 100 expands, additional capacity is needed in the networkcontroller often requiring additional network controller equipment,which becomes increasingly expensive to provide and maintain.Furthermore, sites in the subsystems 110 may be controlled by equipmentlocated at the central network controller 125. When such equipmentfails, the LMR system 100 fails. As such, centralized LMR architecturelacks redundancy and, therefore, is often subject to single points offailure, thereby compromising the integrity of the LMR systemarchitecture.

The present disclosure provides a system and method for providingcommunication in a distributed LMR system architecture. The distributedarchitecture eliminates the need for a central network controller andassociated network equipment. Instead, the functionality of the networkcontroller is distributed among controllers at each of the subsystemscomprising the LMR system, thereby providing peer-to-peer communicationover an internet protocol (IP) network.

FIG. 6 illustrates an example of an LMR system 600 incorporating adistributed architecture in accordance with the present disclosure. Thedistributed LMR architecture 600 provided in FIG. 6 is comprised ofvarious LMR subsystems 610-630 and dispatch stations 650 connected viaIP connections 600 comprising an IP network. In the embodimentillustrated in FIG. 6, the distributed LMR architecture 600 incorporatesfirst and second trunked subsystems 610 and 620 and simulcast subsystems630, however, it should be appreciated that other LMR subsystems may beincluded, such as, for example, conventional, hybrid, multicast, or anyother LMR systems discussed herein.

As mentioned above, the distributed LMR architecture 600 eliminates thecentral network controller and associated equipment that is typicallyprovided with a centralized architecture, and instead distributes thefunctionality of the central network controller and associated equipmentamong subsystem controllers deployed at each of the subsystems 610-630comprising the distributed LMR architecture 600. In some embodiments,the central network controller functionality and associated equipmentmay also be distributed among dispatch stations 650.

As discussed in greater detail below, the distributed LMR architecturedisclosed herein incorporates repeaters, subsystem controllers, networkmanagement systems, and dispatch consoles. In some embodiments, thesecomponents are IP-based and may be managed remotely over the IP network.

Repeaters provide channels/frequencies for over-the-air communicationand, in some embodiments, are equipped with circuitry to provideintegrated voter comparator and simulcast controllerfunctionality/operations.

Subsystem controllers provide interface and gateway functionality forinterconnecting multiple types of LMR subsystems through a common IPnetwork. The subsystem controllers enable dispatch console control oflocal repeaters, provide distributed call control and mobilitymanagement functions, and enable direct routing of calls betweenconventional and trunked systems and/or dispatch consoles withouttalkgroup patching. The distributed architecture of the disclosed systemenables each subsystem controller to perform central network controllerfunctionality for a call originating from its local subsystem, therebyeliminating the need for a dedicated central network controller. Asdiscussed in greater detail below, providing a subsystem controller ateach site in a subsystem provides multi-level redundancy of thecontroller functionality, and allows for communication in case ofequipment or site failure.

Network management systems provide redundant, web-based, and centralizednetwork management functionality for the infrastructure comprising thedistributed architecture system, including the various LMR subsystems(e.g., conventional, trunked, etc.), subsystem controllers, and dispatchconsoles. The network management systems provide management anddeployment of subscriber and talkgroup records; radio administrationincluding radio inhibit, dynamic regrouping, and radio check; agencyspecific management of subscriber records, talkgroup records, andreporting; and pre-defined and custom roles that restrict operatoraccess and activity based on access credentials. The network managementsystems also provide real-time fault monitoring of system components,extensive reports covering system usage and user activities, real-timemonitoring of user and channel activities, and full redundancycapability.

Dispatch consoles provide interoperability via direct IP connection tothe LMR subsystems. In some embodiments, the dispatch consoles areIP-based and fully distributed with no requirement for central controlequipment, thereby allowing extensive scalability and expansion with nosingle point of failure.

Reference is now made to FIG. 7, which illustrates an example embodimentof the first trunked LMR subsystem 610 of FIG. 6. In the exampleembodiment illustrated in FIG. 7, the first trunked subsystem 610comprises a single site trunked subsystem, however, it should beappreciated that the trunked subsystem could include multiple sites. Thetrunked subsystem 610 includes a plurality of repeaters 710 and twosubsystem controllers 720. Each of the repeaters 710 represents achannel (a combination of transmit and receive operations), wherein oneof the repeaters (e.g., 710A) operates a control channel 730, while theremaining repeaters 710 are designated for voice operation.

The trunked subsystem 610 provides redundancy by incorporating twosubsystem controllers 720. One of the subsystem controllers 720 isactive, and the other is on standby. If the active subsystem controller720 fails, then the standby subsystem controller 720 becomes active toprovide a fail-safe transition with no visible impact to the radio users725 and 740. As discussed above, the local subsystem controller 720performs call controls, thereby eliminating the need for a centralcontroller.

In accordance with the embodiment illustrated in FIG. 7, the single sitetrunked subsystem 610 operates in accordance with the following examplefor hosting a call. A radio user 725 initiates a call through thecontrol channel 730. The active subsystem controller 720 processes theuser-initiated call and assigns a voice channel 735 for voicecommunication. The radio users 725 and 740 communicate with each otherover the assigned voice channel 735.

Reference is now made to FIG. 8, which illustrates an example embodimentof the second trunked LMR subsystem 620 of FIG. 6. In the exampleembodiment illustrated in FIG. 8, the second trunked subsystem 620comprises a wide area multicast trunked subsystem. The multicast trunkedsubsystem 620 comprises a plurality of sites 800A-800C connected witheach other to form a wide area trunked system. Each of the sites800A-800C is similar to the single trunked site discussed above withrespect to FIG. 7 and, therefore, includes a plurality of repeaters 810and two subsystem controllers 820. In some embodiments, adjacent sitesin the multicast trunked subsystem 620 operate at a different frequencyto ensure there is no radiofrequency (RF) interference between thesites. However, in some embodiments, frequencies may be reused innon-overlapping sites.

The sites 800A-800C are connected via their respective subsystemcontrollers 820, thereby eliminating the need for a central controller.The subsystem controllers 820 communicate directly with each other tosetup a wide area call between interested sites. For example, a calloriginating from a first site (e.g., site 800A) is transferred to otherinterested sites (e.g., sites 800B and 800C) using the local subsystemcontrollers 820.

In accordance with the embodiment illustrated in FIG. 8, the multicasttrunked subsystem 620 operates in accordance with the following examplefor hosting a call. A radio user 805 from site 800A originates a call.The active subsystem controller 820 in site 800A determines the othersites interested in the call and sends them a call notification 815. Theactive subsystem controller 820 located in each site 800A-800C assigns avoice channel 825 to the call. The active subsystem controller 820 insite 800A transfers the call 835 to the other subsystem controllers 820,and the radios use the assigned voice channel 825 to transmit or receivewithin their respective site.

Reference is now made to FIG. 9, which illustrates an example embodimentof one of the simulcast LMR subsystems 630 of FIG. 6. In the exampleembodiment illustrated in FIG. 9, the simulcast subsystem 630 is atrunked simulcast subsystem, which employs one simulcast control channel915 and one or more simulcast voice channels 925 to provide trunkingcommunication between radio users 905 within the subsystem 630. Eachsite 900 in the simulcast subsystem 630 includes a plurality ofrepeaters 910 (one to provide active or standby control channelfunctionality, or operations, and additional repeaters 910 for eachvoice channel provided in the subsystem 630), and at least one subsystemcontroller 920.

To provide redundancy, a single subsystem controller 920 located at oneof the sites 900 is active for the entire subsystem 630, and theremaining subsystem controllers 920 located at the remaining sites 900serve as standby. Additionally, a single repeater 910 located at one ofthe sites 900 is active to provide control channel functionality, oroperations, and a single repeater 910 located at each of the remainingsites 900 is provided as standby in the event of failure of the activecontrol channel repeater 910. The remaining repeaters 910 located ateach of the sites are generally designated as voice channels for each ofthe channels provided by the subsystem 630, however, each repeater isalso capable of performing voting and simulcast operations as explainedbelow.

The trunked simulcast subsystem 630 employs both voting and simulcastoperations to provide communication across the subsystem 630. In asimulcast operation, a single channel is usually provided by acollection of repeaters 910 distributed across multiple geographic sitescomprising the subsystem (e.g., sites 900A, 900B, and 900C), wherein therepeaters 910 operate on the same frequency pair (transmit and receive),under voted and simulcast configurations, to expand the coverage area ofthe subsystem 630 into the sites (e.g., sites 900A, 900B, and 900C). Inother words, in some embodiments, a single channel may be provided byone repeater 910 at each of the sites 900A-900C in the subsystem 630.

In a traditional simulcast LMR system, the capability of a radio'scommunication to reach the prime site can be limited by the transmitpower of the radio. One way to improve the talkback capability of theradios is to use receiver voting to determine the location (e.g., site)of the radio to determine the best means for communicating with theradio. FIG. 10 provides an example illustration of a traditionalarchitecture for providing receiver voting. Traditionally, receivervoting is performed by placing a number of additional radio receivers(towers) 1010 in strategic locations within the simulcast system 1015 toreceive the RF signal 1020 from a transmitting radio 1025. Each tower1010 then sends the received signal and signal strength data 1035 to avoter comparator 1030. The voter comparator 1030 compares the signalstrength of each received signal and selects the best signal 1040 to usefor communication. The voter comparator 1030 then sends the best signal1040 to the subsystem controller at the prime site for furtherprocessing. By increasing the number of radio receivers within asubsystem, the overall system talkback coverage area may be expanded.

In traditional systems, such as that illustrated in FIG. 10, there isone voter comparator per channel, and the voter comparator is located ata prime site or at the central network controller in a centralized LMRarchitecture, which may not be the same site at which the transmittingradio is located. In these traditional implementations, votercomparators present a single point of failure for a channel.

In accordance with an embodiment of the present disclosure, the singlevoter comparator is eliminated (as is the central network controller),and the voter comparator functionality is integrated into each repeaterin the subsystem. For example, FIG. 11 illustrates an example of such anembodiment wherein repeaters 1110 located at different sites 1115(similar to the repeaters 910 located at the sites 900 in FIG. 9)throughout the subsystem 1130 have integrated voter comparatorfunctionality. Although each of the repeaters 1110 in the subsystem 1130have voter comparator functionality, the voter comparator functionalityof only one of the repeaters 1110 (for a particular channel) isconfigured to be active at any given time. In some embodiments, therepeaters and subsystem controllers communicate with each other todetermine which repeater is active. Additionally, in some embodiments,the network management system may configure a particular repeater to beactive.

The repeater 1110 with active voter comparator functionality may performvoter comparator operations, including voting of signals 1120 for allsites in the subsystem 1130 (for the particular channel assigned to therepeater 1110). The voter comparator functionality of the remainingrepeaters 1110 for the channel are on standby in case of failure of theactive repeater 1110. This redundancy reduces the potential ofoperational downtime because, if the voter comparator functionality ofone repeater 1110 fails, the voter comparator functionality of anotherrepeater 1110 will become active.

If an adequate number of frequencies are not available for communicationin an LMR system, a simulcast operation may be performed to reusefrequencies and cover a large geographic area. Referring again to FIG.9, a simulcast channel may utilize several geographically separatedrepeaters 910 which transmit simultaneously on the same frequency,thereby reducing the number of frequencies needed for the entiresubsystem 630. For example, repeaters 910A, 910B, and 910C located atsites 900A, 900B, and 900C, respectively, may all transmitsimultaneously on the same frequency to provide simulcast communicationbetween radios in the subsystem 630.

In a traditional simulcast LMR system, such as that illustrated in FIG.12, a simulcast channel uses a simulcast controller 1210, whichsynchronizes the launch time (transmit time) of calls transmitted tosites 1220 in the system 1225. The simulcast controller 1210 receivesthe audio signal 1215, assigns a launch time, and then sends the signal1215 to each transmitter/repeater 1230. Each transmitter 1230 transmitsthe signal at its respective site 1220 pursuant to the launch time, andradios 1235 communicating on that channel receive the signal from themultiple transmitters 1230. The timing system implemented by thesimulcast controllers 1210 and transmitters 1230 synchronizes the launchtime in the transmitter 1230 so that calls are transmittedsimultaneously from all sites 1220 for a given repeater channel. Thissynchronization ensures that the transmission on the same frequency isin phase, thereby reducing interference.

In traditional simulcast LMR systems, such as that illustrated in FIG.12, a single simulcast controller 1210 is provided for each channel. Thesimulcast controller 1210 is typically located at a prime site or at thecentral network controller in a centralized LMR architecture.Accordingly, the single simulcast controller 1210 in a traditionalsimulcast LMR system provides a single point of failure for a channel.

In accordance with an embodiment of the present disclosure, the singlesimulcast controller is eliminated (as is the central networkcontroller), and the simulcast controller functionality is integratedinto each repeater in the subsystem. For example, FIG. 13 illustrates anexample of such an embodiment wherein repeaters 1310 located atdifferent sites 1315 (similar to the repeaters 910 located at the sites900 in FIG. 9) throughout the subsystem 1330 have integrated simulcastcontroller functionality. Although each of the repeaters 1310 in thesubsystem 1330 have simulcast controller functionality, the simulcastcontroller functionality of only one of the repeaters 1310 is configuredto be active at any given time. In some embodiments, the repeaters andsubsystem controllers communicate with each other to determine whichrepeater is active. Additionally, in some embodiments, the networkmanagement system may configure a particular repeater to be active.

Referring again to FIG. 9, the repeater 910 with active simulcastcontroller functionality may perform simulcast controller operationsacross all sites 900 in the subsystem 630. In some embodiments, onerepeater 910 may provide simulcast controller functionality for aparticular channel while other repeaters 910 allocated to that channelare on standby to provide redundancy. In other words, one repeater 910for each channel may have active simulcast controller functionality, andthe simulcast controller functionality of the remaining repeaters 910 inthe subsystem 630 are on standby in case of failure of the activerepeater 910 for the standby repeater's respective channel. Thisredundancy reduces the potential of operational downtime because, if thesimulcast controller functionality of one repeater 910 fails, thesimulcast controller functionality of another repeater 910 will becomeactive.

For example, in one embodiment, repeaters 910A, 910B, and 910C areallocated to a particular channel. Repeater 910A may be active toprovide simulcast controller operations for the channel allocated torepeaters 910A, 910B, and 910C, and repeaters 910B and 910C are onstandby. If repeater 910A fails, repeater 910B or repeater 910C maybecome active to provide simulcast controller functionality for thechannel allocated to repeaters 910A, 910B, and 910C.

It should be appreciated that other variations and embodiments may beconsidered within the scope of the present disclosure. For example, insome embodiments, one repeater 910 may provide active simulcastcontroller functionality for more than one channel in the subsystem 630.In this embodiment, the active simulcast repeater 910 may providesimulcast controller functionality for some, or all, of the channels inthe subsystem 630. For example, repeater 910A may be allocated to afirst channel, repeater 910B allocated to a second channel, and repeater910C allocated to a third channel. Repeater 910A may provide activesimulcast controller functionality for the first channel, secondchannel, third channel, or any combination thereof, and the remainingrepeaters 910B and 910C may operate in standby mode.

In accordance with an embodiment of the present disclosure, the trunkedsimulcast subsystem 630 may operate in accordance with the followingexample call sequence discussed with reference to FIG. 9. A radio 905Ainitiates a call through the control channel 915. The active subsystemcontroller 920 (e.g., subsystem controller 920 in site 900A) processesthe user-initiated call and assigns a voice channel 925 for the call.The radio users 905 communicate with each other over the voice channel925. Any request from the initiating user 905A is received by one ormore repeaters 910 of the channel, and the repeater 910 with activevoter comparator functionality (e.g., repeater 910A) then performs thevoter comparator operation to select the best signal. Additionally, anydata packet sent to the initiating user 905A or other radio users 905 issent to all repeaters 910 of the channel 925 through the repeater 910with active simulcast controller functionality (e.g., repeater 910A).The repeaters 910 then simultaneously transmit the data to the radios905 over the channel 925. In the embodiment discussed herein, both thevoter comparator and simulcast controller functionality is provided by asingle repeater (910A). However, it should be appreciated that, in someembodiments, the voter comparator functionality and simulcast controllerfunctionality may be provided by separate repeaters.

As discussed above and illustrated in FIG. 14, traditional simulcast LMRsystems 1400 include a prime site 1410, which hosts voter comparators,simulcast controllers, and a simulcast subsystem controller, therebyproviding simulcast synchronization and voter comparator functionalityfor all channels in the system 1400. The traditional simulcast LMRsystem 1400 embodies a centralized architecture, wherein the prime site1410 acts as a central network controller for all sites 1420 in thesystem 1400. Thus, each site 1420 relies on the constant availability ofthe prime site 1410, and is therefore susceptible to loss of thesimulcast and voter comparator functionality in the event of prime sitefailure.

Referring now to FIG. 15, and in accordance with the forgoing discussionof the present disclosure, the trunked simulcast subsystem 1500 of thedistributed LMR architecture eliminates the need for a dedicated primesite or prime site controller. The availability of simulcast controllerfunctionality and voter comparator functionality in each repeaterenables the distribution of the prime site functionality of each channelto different sites 1510 in the subsystem 1500. Accordingly, any repeatermay provide prime site functionality/operations for a channel, whereinproviding prime site functionality/operations for a channel includesproviding simulcast controller functionality (i.e., performing simulcastcontroller operations) and/or providing voter comparator functionality(i.e., providing voter comparator operations) for the channel. Primesite functionality of each repeater may be assigned throughconfiguration, or dynamically. For example, as shown in FIG. 15, a firstsite 1510A may provide prime site functionality for a first channel, asecond site 1510B may provide prime site functionality for a secondchannel, a third site 1510C may provide prime site functionality for athird channel, and a fourth site 1510D may provide prime sitefunctionality for a fourth channel. Other repeaters in the subsystem1500 are configured as standbys and become active upon failure of theprimary repeater (i.e., the repeater providing active votercomparator/simulcast controller functionality).

As illustrated in FIGS. 9 and 15, the distributed simulcast architecturealso eliminates the need for a central controller to process calls.Instead, the trunked simulcast subsystem controller (920) performscontrol for all calls. If the primary subsystem controller fails, one ofthe standby subsystem controllers becomes active, thereby providingredundancy and improved reliability in comparison to a centralizedarchitecture.

Referring briefly to FIG. 6, the dispatch centers 650 include dispatchconsoles connected to other components/subsystems in the distributed LMRarchitecture system 600. Each console is peer to other consoles in thesystem 600 and is fully distributed, thereby ensuring that the impact ofa console failure is localized to the corresponding dispatch center 650,and does not affect the remaining components/subsystems in the system600.

Reference is now made to FIGS. 16-18, which are provided in support ofthe following description of various redundancy advantages provided bythe disclosed distributed simulcast LMR architecture. Specifically, thedisclosed distributed simulcast architecture provides redundancy in atleast three aspects: (i) simulcast controller and voter comparatorredundancy, (ii) network failure redundancy, and (iii) site redundancy.

FIG. 16 illustrates an example embodiment demonstrating simulcastcontroller and voter comparator redundancy in the disclosed distributedsimulcast LMR architecture. As illustrated in the example embodiment inFIG. 16, simulcast controller functionality and voter comparatorfunctionality is shown distributed between multiple simulcast sites 1615in a distributed simulcast subsystem 1610. In the subsystem 1610A, sites1615A, 1615B, 1615C, and 1615D provide prime site functionality forchannels one, two, three, and four, respectively, and site 1615D alsoprovides the active subsystem controller. In subsystem 1610B, therepeater providing the simulcast controller/voter comparatorfunctionality at site 1615A fails, and the prime site functionality forchannel one changes to one of the standby repeaters located at one ofthe other sites. In this example, site 1615C assumes prime sitefunctionality for channel one. As shown in the subsystem 1610B, site1615C provides prime site functionality for channels one and three. Inthe embodiment illustrated in FIG. 16, the subsystem controller locationat site 1615D remains unchanged.

FIG. 17 illustrates an example embodiment demonstrating network failureredundancy in the disclosed distributed simulcast LMR architecture. InFIG. 17, a trunked simulcast subsystem 1700 includes sites 1715A, 1715B,1715C, and 1715D providing prime site functionality for channels one,two, three, and four, respectively, and site 1715D also providing theactive subsystem controller for the subsystem 1700. As illustrated inFIG. 17, if a network failure breaks the trunked simulcast subsystem1700 into halves 1710 and 1720, each half becomes a smaller simulcastsubsystem.

One of the subsystem controllers in each of the smaller subsystems 1710and 1720 becomes active and continues to provide user communication on areduced number of channels. For example, in the first reduced subsystem1710, the subsystem controller at site 1715A becomes active and providescall control functionality for sites 1715A and 1715C. In the secondreduced subsystem 1720, the subsystem controller at site 1715D remainsactive and provides call control functionality for sites 1715B and1715D. This built-in redundancy ensures that users in each half 1710 and1720 can still communicate with each other without interfering with RFsignals in the overlapping area.

FIG. 18 illustrates an example embodiment demonstrating site redundancyin the disclosed distributed simulcast LMR architecture. In FIG. 18, atrunked simulcast subsystem 1800 includes sites 1815A, 1815B, 1815C, and1815D providing prime site functionality for channels one, two, three,and four, respectively, and site 1815A also providing the activesubsystem controller for the subsystem 1800. Site redundancy is enabledby the combination of redundant simulcast controller functionality andvoter comparator functionality in each repeater and a redundantsubsystem controller at each site 1815. Therefore, in case of acatastrophic failure of a site 1815, the rest of the sites 1815 continueto provide coverage with little impact on the subsystem 1800. Forexample, as shown in FIG. 18, if site 1815A experiences a catastrophicfailure, one of the standby repeaters located at one of the other sites(in this example, site 1815C) is activated and assumes prime sitefunctionality for channel one. Additionally, one of the standbysubsystem controllers located at one of the other sites (in thisexample, site 1815D) is activated and becomes the subsystem controllerfor the subsystem 1800.

When compared to centralized LMR system architecture and traditionalsimulcast LMR systems, the foregoing disclosure of the distributedsimulcast architecture provides various advantages and benefits. Forexample, the disclosed system provides increased reliability because theremoval of a prime site eliminates the single-point-of-failure structureprovided in a traditional simulcast system. Furthermore, distributingthe functionality of the prime site to the various sites and equipmentcomprising the distributed simulcast subsystem reduces costs andmaintenance required to maintain the system. Additionally, providing asubsystem controller at each site in the subsystem offers multiplelevels of redundancy of the controller, and affords communicationthroughout the subsystem even in the event of various failures. Finally,providing voter comparator and simulcast controller functionality ineach repeater provides N times the voter/simulcast controlleravailability in a traditional simulcast system, where N represents thenumber of sites in the subsystem. This also allows redundancy of votercomparator functionality and simulcast controller functionality within asite or across multiple sites (to survive network failure, site failure,or equipment failure), thereby providing communication in the event ofmultiple failures, and providing automatic and dynamic tuning oftransmission launch time.

A number of additional and alternative embodiments of the disclosedsystem and method may be provided without departing from the spirit orscope of the present disclosure as set forth in the claims providedherein. These various embodiments are believed to be understood by oneof ordinary skill in the art in view of the present disclosure.

What is claimed is:
 1. A system for providing communication in adistributed land mobile radio (LMR) system architecture, the distributedLMR system architecture comprising one or more subsystems incommunication with a data network, the system comprising: one or moreLMR sites for providing radio communication among land mobile radiosassociated with the system, the one or more LMR sites comprising atleast one of the one or more subsystems; one or more subsystemcontrollers disposed at each of the one or more LMR sites comprising theat least one subsystem, each subsystem controller having at least anactive mode and a standby mode, wherein at least one subsystemcontroller is operable in the active mode to control communicationbetween one or more of the land mobile radios and to controlcommunication between the one or more LMR sites in the at least onesubsystem; and one or more repeaters disposed at each of the pluralityof LMR sites in the at least one subsystem, each of the repeatersoperable to provide a communication channel for at least one of the landmobile radios to communicate with one or more of the LMR sites in thesystem, wherein each repeater has at least an active mode and a standbymode, and wherein at least one repeater is operable in the active modeto initiate at least one of a voter comparator operation and a simulcastcontroller operation using a simulcast controller, and wherein thesimulcast controller operation includes assigning a launch time, andsending a signal to repeaters sharing a given repeater channel at otherLMR sites whereby a radio call is transmitted simultaneously at theassigned launch time and in phase by the repeaters sharing the givenrepeater channel.
 2. The system as set forth in claim 1, wherein thevoter comparator operation includes comparing a strength of one or morereceived signals to determine a strongest signal to use forcommunication among two or more land mobile radios associated with thesystem.
 3. The system as set forth in claim 1, wherein a repeater in theactive mode is configurable to perform the simulcast controlleroperation for the communication channel provided by the repeater in theactive mode.
 4. The system as set forth in claim 1, wherein a repeaterin the active mode is configurable to perform the simulcast controlleroperation for a communication channel provided by a different repeater.5. The system as set forth in claim 4, wherein the communication channelprovided by the repeater in the active mode is a first frequency, andthe communication channel provided by the different repeater is a secondfrequency different than the first frequency.
 6. The system as set forthin claim 1, wherein repeaters in a standby mode are configurable toswitch to the active mode upon failure of a repeater operating in theactive mode.
 7. The system as set forth in claim 1, wherein subsystemcontrollers in a standby mode are configurable to switch to the activemode upon failure of a subsystem controller operating in the activemode.
 8. The system as set forth in claim 1, wherein subsystemcontrollers in a standby mode are configurable to switch to the activemode upon failure of at least a portion of the one or more sitescomprising a subsystem controller operating in the active mode.
 9. Thesystem as set forth in claim 1, wherein the subsystem controller isfurther configurable to provide communication between two or moresubsystems comprising the distributed LMR system architecture.
 10. Thesystem as set forth in claim 1, wherein the data network is an InternetProtocol network.
 11. The system as set forth in claim 1, wherein the atleast one subsystem is a simulcast subsystem.
 12. A method for providingcommunication in a distributed land mobile radio (LMR) systemarchitecture, the distributed LMR system architecture comprising one ormore subsystems in communication with a data network, the methodcomprising: providing a plurality of LMR sites for providing radiocommunication among land mobile radios associated with the distributedLMR system architecture, the plurality of LMR sites comprising at leastone of the one or more subsystems; providing a subsystem controller ineach of the plurality of LMR sites comprising one of the subsystems,each subsystem controller having at least an active mode and a standbymode; operating one of the subsystem controllers in the active mode tocontrol communication between the plurality of LMR sites and to controlcommunication between one or more of the land mobile radios; operatingthe remaining subsystem controllers in the standby mode; providing aplurality of repeaters at each of the plurality of LMR sites comprisingthe subsystem, each repeater having at least an active mode and astandby mode; operating at least one of the repeaters in the active modeto perform at least one of a simulcast controller operation and a votercomparator operation; operating the remaining repeaters in the standbymode, and wherein the simulcast controller operation comprises assigninga launch time, and sending a signal to repeaters sharing a givenrepeater channel at other LMR sites whereby a radio call is transmittedsimultaneously at the assigned launch time and in phase by the repeaterssharing the given repeater channel.
 13. The method as set forth in claim12, wherein performing the voter comparator operation includes comparinga strength of one or more received signals to determine a strongestsignal to use for communication among two or more land mobile radiosassociated with the distributed LMR system architecture.
 14. The methodas set forth in claim 12, further comprising providing a communicationchannel via one or more of the repeaters.
 15. The method as set forth inclaim 14, further comprising performing the simulcast controlleroperation for a communication channel provided by the repeater operatingin the active mode.
 16. The method as set forth in claim 14, furthercomprising performing the simulcast controller operation for acommunication channel provided by a different repeater.
 17. The methodas set forth in claim 16, wherein the communication channel provided bythe repeater operating in the active mode is a first frequency, and thecommunication channel provided by the different repeater is a secondfrequency different than the first frequency.
 18. The method as setforth in claim 12, further comprising switching a repeater from thestandby mode to the active mode upon failure of a repeater operating inthe active mode.
 19. The method as set forth in claim 12, furthercomprising switching a subsystem controller from the standby mode to theactive mode upon failure of a subsystem controller operating in theactive mode.
 20. The method as set forth in claim 12, further comprisingswitching a subsystem controller from the standby mode to the activemode upon failure of the LMR site comprising a subsystem controlleroperating in the active mode.
 21. The method as set forth in claim 12,further comprising providing communication, via a subsystem controller,between two or more subsystems comprising the distributed LMR systemarchitecture.
 22. The method as set forth in claim 12, wherein thesubsystem is a simulcast subsystem.